as far as I know there is noone working on a Java API so far. Using Jacob (or a similar COM Wrapper) is the right way, I would think.
Probably it is a good start to have a look at the COM samples, that give a general overview on the COM Interface. After that, it probably makes sense to look at the VB code of the COM Class itself and then start doing the Wrapper with Jacob.
Unfortunately, this has to work on Linux so I can't use any printer driver solution. Besides that, this is a J2EE web application, so what I need it to do is, when the user clicks a button a Struts Action is called that loads any number of Word docs from the database and converts them to PDF. So what I really need is an API, not a driver or a 3rd-party application.